1. Field of the Invention
The present invention relates generally to stepping motors, and more particularly to a vibration-proof stepping motor with a built-up stator which is suitable for an automated assembling.
2. Description of the Prior Art
Conventionally, stepping motors include a stator and a rotor disposed in a housing and assembled together in a built-up construction by means of screw fasteners. With this screwed assembly, stator cores are prevented from interfering with each other.
For a purpose of automated assembling, various attempts have been proposed to construct stator cores which can be assembled layerwise without using screw fasteners. One such proposed stator core construction is a so-called "claw-pole" construction. In the case of the conventional construction, when a stator coil is energized, the assembled stator cores tend to oscillate in resonance with the excited stator coil, thus generating unpleasant noises.
U.S. Pat. No. 5,043,613 discloses vibration isolating dampers disposed between adjacent stator cores for solving the noise problem. The disclosed dampers are satisfactory in terms of vibration isolating effect. However, in terms of automated assembling, they needs an additional damper positioning and mounting operations which must be performed with accuracy. There is a demand for a stepping motor which is suited for automated assembling and is capable of reliably isolating vibrations and vibration-induced noises without increasing the number of components.